First step:
In $J2EE_HOME/bin/userconfig.sh,
uncomment
#CLASSPATH=
#export CLASSPATH
and change into
CLASSPATH=$CLASSPATH:/pathtoyourmysqljar/mm.mysqljar-2.0.14-bin.jar
export CLASSPATH
then,
Second step:
On command line, type something similar(as you prefer)
>j2eeadmin -addJdbcDriver jdbc/Mysql org.gjt.mm.mysql.Driver
>j2eeadmin -addDataSource jdbc/Mysql org.gjt.mm.mysql.jdbc2.optional.MysqlDataSource
Hope it help you,
Bye